ORGN 897 |
| We proposed a condensation-enolization-cyclization cascade reaction to couple two simple fragments that lead to the stereoselective synthesis of highly functionalized carbocycles. While executing this proposal, we achieved a cascade reaction sequence that leads to highly functionalized cyclohexenones starting from reaction of cyclobutenones with lithio-unsaturated sulfones and amides. The hexatriene-cyclohexadiene cyclization steps presumed to be involved are among the most facile hexatriene electrocyclizations reported thus far. Then we integrated cyclizations with soft enolizations and successfully accomplished direct chemoselective cyclizations of divinyl ketones to cyclohexenones mediated by a sterically demanding Lewis acid and an amine base under mild reaction conditions. The methodology was then extended to highly diastereoselective cycloisomerization reactions that produce functionalized cyclooctatrienes under mild reaction conditions. The scope and mechanism of this process was extensively studied. The asymmetric version and 3-step tandem is under investigation with positive preliminary results.
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New Reactions and Methodology
8:00 AM-11:40 AM, Thursday, 14 September 2006 Moscone Center -- Room 133, Oral
Division of Organic Chemistry |